Do not report cpu limited resolution stats when degradation preference is disabled and no scaling is done.

When degradation preference is kDegradationDisabled, do not update WebRTC.Video.CpuLimitedResolutionInPercent.

BUG=webrtc:6634

Review-Url: https://codereview.webrtc.org/2807133002
Cr-Commit-Position: refs/heads/master@{#17757}
diff --git a/webrtc/video/send_statistics_proxy_unittest.cc b/webrtc/video/send_statistics_proxy_unittest.cc
index e2cb2fd..edb7564 100644
--- a/webrtc/video/send_statistics_proxy_unittest.cc
+++ b/webrtc/video/send_statistics_proxy_unittest.cc
@@ -841,7 +841,22 @@
   EXPECT_EQ(1, metrics::NumEvents("WebRTC.Video.SentFramesPerSecond", kFps));
 }
 
-TEST_F(SendStatisticsProxyTest, CpuLimitedResolutionUpdated) {
+TEST_F(SendStatisticsProxyTest, CpuLimitedHistogramNotUpdatedWhenDisabled) {
+  const int kNumDownscales = -1;
+  statistics_proxy_->SetQualityScalingStats(kNumDownscales);
+
+  for (int i = 0; i < SendStatisticsProxy::kMinRequiredMetricsSamples; ++i)
+    statistics_proxy_->OnIncomingFrame(kWidth, kHeight);
+
+  statistics_proxy_.reset();
+  EXPECT_EQ(0,
+            metrics::NumSamples("WebRTC.Video.CpuLimitedResolutionInPercent"));
+}
+
+TEST_F(SendStatisticsProxyTest, CpuLimitedHistogramUpdated) {
+  const int kNumDownscales = 0;
+  statistics_proxy_->SetCpuScalingStats(kNumDownscales);
+
   for (int i = 0; i < SendStatisticsProxy::kMinRequiredMetricsSamples; ++i)
     statistics_proxy_->OnIncomingFrame(kWidth, kHeight);